TSST-1 protein exerts indirect effect on platelet activation and apoptosis.

Thrombocytopenia or platelet dysfunction is a risk factor for severe infection. () releases a variety of virulence factors especially toxic shock syndrome toxin 1 (TSST-1), which may cause toxic shock syndrome. , when carrying the gene, is more prone to cause toxic shock syndrome and is responsible for an especially high rate of mortality. However, the effect of TSST-1 protein on platelets is unknown. Patients with the gene positive bacteremia showed more serious infection, higher mortality and lower platelet count. The gene positive strains induce more platelet apoptosis and activation and corresponding up-regulation of Bak and down-regulation of Bcl-XL in addition to the activation of Caspase-3. C57BL/6 mice infected with the gene positive strains resulted in both a decrease in platelet count and an increase in platelet apoptosis and/or activation events and mortality. Moreover, TSST-1 protein, encoded by gene, caused the decrease of platelet count, the increase of platelet apoptosis and activation events and the level of inflammatory cytokines . However, TSST-1 protein was unable to induce traditional activation and apoptosis on human platelets . These results suggested that TSST-1 protein may exert indirect effects on platelet activation and apoptosis .